Answer:
Iodine has the greatest average number of neutrons.
Step-by-step explanation:
Tin
Tin has 41 isotopes with every mass number from 99 to 139. Thus, the average mass number is 119.
Tin has atomic number 50, so the average number of neutrons
is 119 – 50 = 69.
Antimony
Antimony has 37 isotopes with every mass number from 103 to 139. Thus, the average mass number is 121.
Antimony has atomic number 51, so the average number of neutrons
is 121 – 51 = 70.
Tellurium
Tellurium has 39 isotopes with every mass number from 104 to 142. Thus, the average mass number is 123.
Tellurium has atomic number 52, so the average number of neutrons
is 123 – 52 = 71.
Iodine
Iodine has 37 isotopes with every mass number from 108 to 144. Thus, the average mass number is 126.
Iodine has atomic number 53, so the average number of neutrons
is 126 – 53 = 73.
Iodine has the greatest average number of neutrons.
